The invention relates to power distribution apparatus and methods and, more particularly, to transformer apparatus and methods.
There is an ongoing quest for increased energy efficiencies in data centers and similar facilities. One technique for increasing efficiency is to increase the voltage used for power distribution in a facility. For example, current computer power supplies commonly can operate from 230V without modification. Replacing a 120/208V wye distribution system in a data center with a 230/400V wye system could allow elimination of isolation transformers used to step down to 120/208V, thus eliminating the approximate 2% loss associated with the isolation transformers.
In the U.S., however, facility power distribution systems commonly are 480V delta and, in rarer cases, 277/480V wye. Computer power supplies commonly cannot operate at 480V or 277V. Thus, provision of power to such devices may require either modification of the power supplies or conversion of the AC input to 230/400V wye.
A common approach illustrated in FIG. 1 is to use a delta-wye isolation transformer 10 to converter from 480V delta to 230/400V wye. This solution, however, typically comes at the cost of lost efficiency.
Another technique, illustrated in FIG. 2, involves using a zigzag transformer 20, which creates a neutral, and a separate autotransformer 30, which provides a voltage transformation. As illustrated in FIG. 3, the zigzag transformer 20 creates a synthetic neutral Ho relative to phase conductors H1, H2, H3. The zigzag transformer 20 includes windings 42a, 42b, 42c wound on respective cores 50a, 50b, 50c. The winding 42a is connected to a winding 44b on the core 50b, the winding 42b is connected to a winding 44c on the core 50c, and the winding 42c is connected to a winding 44a on the core 50a. 